1. Field of the Invention
The present invention relates to a lens driving apparatus for electrically driving a lens in the optical axial direction, which is used in a power focusing apparatus, a power zooming apparatus or the like that controls the focus or the angle of view of a camera lens by means of the driving force of a motor.
2. Description of the Related Art
There are various types of conventional power focusing apparatus and power zooming apparatus which drive a motor in accordance with the amount of operation of a manually operatable operation member and the operational direction thereof, and drive a lens in the optical axial direction by means of the driving force of the motor. In the view point of manual operation of the operation member, these apparatuses are classified into a type having an operation member constituted by a press-button switch as disclosed in the Japanese Patent Disclosure (KOKAI) No. 51-13236, and a type having an operation member constituted by a rotational member such as a focus ring provided around a lens body or the like as disclosed in the Japanese Patent Disclosure (KOKAI) Nos. 63-89823 to 63-89826. Since the operation member need not be mechanically coupled to the lens driving mechanism in those apparatuses, the operation member may be located on the camera body instead of on the lens body.
Suppose that, at a time of adjusting the focus, a photograghing object which should be focused is located slightly closer than the closest photographing distance of a camera lens. With the use of a conventional camera having a mechanical focus adjusting mechanism, a focusing ring is pressed against a closest end stopper while the focusing ring is being rotated so that it cannot be further rotated. This permits a photographer to recognize that the lens has been pressed against the closest end. In a case of a power focusing apparatus, by way of contrast, the operation member and lens driving mechanism are disposed independent from each other, not mechanically coupled together, and the operation member can be operated in endless manner. If the lens is pressed against the closest end and stopped there, therefore, the operation member would not be pressed against anywhere, nor would it be stopped at all. Accordingly, a photographer who is looking through the finder is likely to continue the power-focusing operation without being aware of the lens' pressing against the closest end. The photographer may become aware of this event after continuing this operation a little while. This may make the photographer to feel very inconvenient and to lose a good shutter chance.
Similar inconvenience would certainly occur when a power zooming apparatus is used. For instance, if the photographer continues a zooming operation in order to zoom up a photographing object, the angle of view may not change since the zoom lens is pressed against the long focal distance end. An example of the conventional power zooming apparatus displays the driving direction of a zoom motor within the finder while the motor is being driven (as disclosed in the Japanese Patent Disclosure (KOKAI) No. 51-13236). In this apparatus, even if the lens is pressed against the stopper, the display is kept ON as long as the driving instruction continues, and the above problem will not be overcome.